Andre Agassi, 42, won eight Grand Slam championships and an Olympic gold medal during his career (1986-2006).

Steffi Graf, 43, of Germany, has 22 Grand Slam singles titles (1982-1999). She is the only player to achieve a Calendar Grand Slam, winning all majors on four different types of tennis court (1993-1994). Graf has an Olympic gold medal as well. She has a son and a daughter with husband Andre Agassi.

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Monica Seles, 38, has won eight Grand Slam titles for her native country, Yugoslavia, and one more championship as a U.S. citizen (1989-2003). In 1990, Seles became the youngest ever French Open champion at age 16. After a series of wins over Steffi Graf, Seles was stabbed in the back during a game by a crazed Graf fan in 1993. Seles took a two-year break before returning to the court.

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Lindsay Davenport, 36, has three different Grand Slam singles titles and three Grand Slam doubles titles, and she is an Olympic gold medalist (1993-2011.) She is not technically retired yet and still competes, but she has been taking several breaks over the last six years to give birth to her three children.

Martina Hingis, 31, of Switzerland, has five Grand Slam singles titles, nine women's doubles titles, and one mixed doubles title (1994-2006). At Wimbledon, she became the youngest player to win a Grand Slam title at age 15 in 1996.

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Boris Becker, 45, of Germany, has six Grand Slam singles titles, an Olympic gold medal in doubles (1984-1999). He is the youngest-ever winner of the men's singles title at Wimbledon at the age of 17.

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Stefan Edberg, 46, of Sweden, is the only player to reach a 'Junior Grand Slam,' winning all majors at a junior level. He won six Grand Slam singles titles and three Grand Slam men's doubles titles (1983-1996). Edberg is the childhood idol of Roger Federer.

Björn Borg, 56, of Sweden, won 11 Grand Slam singles titles (1973-1984). After almost going bankrupt after he retired, Borg launched the Bjorn Borg fashion label, which is the second most popular fashion company in Sweden after Calvin Klein.

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Czech-born Ivan Lendl, 52, won eight Grand Slam singles titles (1978-1994). After he retired at 34, Lendl became an avid golfer and even won the Celebrity Tour. Lendl started coaching British tennis player Andy Murray in 2012.

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Jimmy Connors, 60, has eight Grand Slam singles titles and two Grand Slam doubles titles. Connors won a record 109 ATP tournaments, 15 more than Ivan Lendl, and over 30 more than Roger Federer and John McEnroe (1972-1996).

Michael Chang, 40, is the youngest ever male player to win the French Open at age 17 in 1989. It will be his only Grand Slam title (1988-2003). Chang has 34 career titles in total. After tennis, he became an avid fisherman.

Patrick Rafter, 39, of Australia, won the U.S. Open two years in a row. His other Grand Slam title is a win from the Australia Open doubles (1991-2002).

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Jennifer Capriati, 36, is the youngest ever player to break into the top 10 at age 14. She has three Grand Slam singles titles, and an Olympic gold medal from the 1992 Barcelona games (1990-2004).

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Arantxa Sánchez Vicario, 40, of Spain, has a series of Grand Slam wins – four singles, six women's doubles, and four mixed doubles titles; and she has two silver and two broze Olympic medals (1985-2002).

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Mary Pierce, 37, has four Grand Slam titles, two in singles and two in doubles (1989-2005). Pierce started playing tennis at age 10, and only two years later became the U.S. national 12-and-under junior champion.

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Chris Evert, 57, won 18 Grand Slam singles championships, including a record seven championships at the French Open and a record six championships at the U.S. Open. Evert's career winning percentage in singles matches of 90.05% (1309–145) is the best in the history of professional tennis, man or woman. (1972-1989)

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Gabriela Sabatini, 42, of Argentina, won two Grand Slam titles (one is singles and one in doubles), and a silver Olympic medal (1985-1996).

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Jana Novotna, 44, of the Czech Republic, has a Grand Slam singles title from Wimbledon and has also won 12 Grand Slam women's doubles titles and four Grand Slam mixed doubles titles. She has three Olympic medals - a bronze in singles, and two silver medals in doubles. (1987-1999)

Ilie Nastase, 66, of Romania, has seven Grand Slam titles – two in singles, three in men's doubles, and two in mixed doubles (1969-1985). He was the first professional sports figure to sign an endorsement contract with Nike in 1972.

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Guillermo Vilas, 60, of Argentina, was a clay-court specialist and won four Grand Slam titles (1969-1992).

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Goran Ivanisevic, 40, of Croatia, is the only person to win the men's singles title at Wimbledon and a wildcard. It's his only Grand Slam title (1988-2004). He also has two bronze Olympic medals. After retiring from tennis, Ivanisevic started playing soccer for a Croatian team.

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Margaret Court, 70, of Australia, dominated women's tennis in the 1960s. She won a record 24 Grand Slam singles titles, and also 19 women's doubles and 19 mixed doubles titles, giving her a record of 62 major titles overall (1960-1977). Court became a Pentecostal Christian minister and a vocal critic of LGBT rights.

John McEnroe, 53, won seven Grand Slam singles titles (three at Wimbledon and four at the US Open), nine Grand Slam men's doubles titles, and one Grand Slam mixed doubles title (1978-1992).

Anna Kournikova, 31, of Russia, was one of the most popular tennis players in late 1990s and early 2000s, despite never winning a major singles title. She has two Grand Slam doubles titles (with Martina Hingis), and reached No. 1 ranking in doubles in 2000.